Tectonics, science task 4

Question 1

Outline Alfred Wegener’s theory of continental drift.

Answer 1

• 1912 German meteorologist and geophysicist.
• claimed that the continents were once connected to each other and that they were once a large land mass called pangaea, so the continents must have somehow seperated and drifted across the oceans.
• this is what he called continental drift.

Question 2

continental drift support: the shape of continents.

Answer 2

• the continents seemed to fit like a jigsaw, especially South america and Africa.

Question 3

continental drift support: fossil evidence.

Answer 3

• same fossils of prehistoric species were found on continents far apart.
• so he thought that the continents shifted, taking the fossils with the,.
• he rearranged the continents so the distribution of the mossils matched up across the continents.

Question 4

Outline Hess’s theory of sea floor spreading

Answer 4

• 1962 American geologist Harry hess.
• used sonar to map the bottom of the pacific ocean
• he saw underwater mountains
• he propsed: new crust was being formed at the ocean ridges and spreading outwards- seafloor spreading.
• the crist was sinking down into the earth to form ocean trenches- subduction

Question 5

Proving seafloor spreading. - magnetic stripping.

Answer 5

• when molten rock solidifies magnetites line up with the magnetic field of the earth.
• the earths magnetic field changes and is preserved in the rock as it forms
• patterns and strips of rock with alternating magnetism are symmetrical on either side of the mid-ocean ridge.
• supports new seafloor being added equally on either side of the ridge.

Question 6

Proving seafloor spreading- age of the sea floor.

Answer 6

• the further the rocks of the sea floor are from the are from the mid ocean ridges, the older they are

so: new rock forming near the ridges move outward away from the ridge.

Question 7

Proving seafloor spreading- sediment thickness.

Answer 7

• sedimentary rocks are thicker therefore sediments falling for longer on the rocks on the sea floor, further away from the ridges.

Question 8

use a model to demonstrate sea floor spreading.

Answer 8

(look at the book)
1) at the mid-ocean, tectonic plates diverge.
2) Magma rises from the asthenosphere to fill the gaps creating anew oceanic crust.
3) As new crust forms old crust is pushed away from the edge.
4) the lithosphere moves on top of the flowing asthenosphere, causing the plates to spread apart.

Question 9

Theory of plate tectonics.

Answer 9

• explains how the earths outer shell (lithosphere) is divided into several large, rigid plates that flow on the semi-fluid asthenosphere beneath.
• tectonic plates move and interact at their boundaries to cause geological activites.

Question 10

Theory of plate tectonics, recent evidence, Gps

Answer 10

• GPS Global Positioning system
• meausres the precise movement of tectonic plates and how fast they are moving,

Question 11

theory of plate tectonics, recent evidence, eathquake positioning

Answer 11

Earthquake positioning
- earthquakes occring at the boundaries of plates supporting that tectonic plates are responsible for them

Question 12

theory of plate tectonics recent evidence radiometric dating.

Answer 12

radiometric dating
- shows that the youngst oceanic rocks are at mid-ocean ridges indicating that new crust is formed and supporting the seafloor spreading
- dating rocks in subduction zones confirms that older oceanic crust is recycles back into the amnte.
- rocks in mountain ranges reveal where the tectonic plates have collided
- volcanic activity reveals connection between tectonic activity and volcanic erruption.

Question 13

mechanics of movement- convection currents

Answer 13

convection currents
- theory on how plates move on the asthenosphere
- plates are dragged along as hot magma in the asthenosphere rises up and flows under the plates = convectional currents
- as the liquid rock flows friction between it and the tectonic plate causes movement.

Question 14

mechanics of movement- gravity. (slab pulling)

Answer 14

• plates of subductions zones(region where one tectonic plate is forced bentath another)are denser than the ones at the mid ocean ridges.
  theory: gravity pulls the heavy and denser plate donwards into the subduction zone and pulls the plate into the trench and away from the ocean ridges.
• so the plates are pulled apart.

Question 15

mechanics of movement- gravity. (ridge push)

Answer 15

• new oceanic crust forming at the ridgs aboce the rest of the crust.
• gravity pulls the new crust downwards.
• this would push on the older crust below and to its side, so the plates move sideways.

Question 16

mechanics of movement- rifting and continental drift.

Answer 16

Proposed: rifting occurs hen the earths crust cracks and subsides, allowing water to fill the gap.
- new crust forms at the mid ocean ridge and pushes the continents and ocean floor.
- explaines wegners idea of drifting continents.

Question 17

explain the importance of convetion currents in the movement of earths tectonic plates.

Answer 17

• transfer heat from the earths interior, cuasing hot magma to rise, pushes plates apart at mid ocean ridges, cooler slabs sink into the subduction zones, pulling plates together.
• generates force that drives plates and geological activities
• contributes to recucling oceanic and continental crust=seafloor spreading and subduction.

Question 18

type of interactions and examples, diverging boundaries.

Answer 18

-tectonic plates move apart in opposite directions
- leaves a rift(a deep crack)
- magma from the asthenosphere rises up into the rift and solidifies as it cools: new crust is formed
CONSTRUCTIVE.

e.g. Mid-atlantic ridge running through iceland
- the island is widening as new crust forms
- 2-5 cm per year, bc constant volcanic eruptions cause magma to spew into the rift.

Question 19

type of interactions and examples, converging boundaries.

Answer 19

• two plates collide head on wit each other
• rock is destroyed: DESTRUCTIVE
• forms mountains, island chaines, underwater trenches which depends on what types of crust collide.

Question 20

Converging boundaries: mountains, volcanoes and trenches.

Answer 20

• oceanic crust colliding with continental crust result in the denser oceanic plate subduct.
• subduction of denser continental plate= fold mountains and volcanoes.
• deep ocean trenches form at the subduction zone.

e.g. Nazca plate colliding with the South American plante = the andes mountains and peru chille trench
- subducting plate sinks into the how mantle, heat from friction, melting point, forming magma and destruction of oceanic crust.

Question 21

Converging boundaries: island arcs

Answer 21

• oceanic plates collide, faster moving plate subducts, forming deep tranches.
• descending plate melts into magma
• magma rises to the surgace to creat a chain of volcanic islands.

e.g. mariana trench and island arc
- Pacific ocena ollided with the Mariana plate
- result a string of volcanic islands form an island along the boundaries of these plates.

Question 22

Converging boundaries: high mountain systems.

Answer 22

• two continental plates collide and both are pushed up since neither is denser than the other
• the high mountain system is created

e.g. Himalayas:
Indian plate and the eurasian plate collision results in the Himalayas.

Question 23

type of interactions and examples, transform boundaries.

Answer 23

• two tectonic plates slide parallel to each other in opposite directions
• move slowly but can suddenly flip and turn into earthquakes
• Boundaries often have fold mountains and fault lines(cracks in the rock)
• fault cracks= numerous parallel lines.

e.g. San Andreas Fault:
= Pacific plate and the NA plate fault
- near Los angelos and san fransisco
- significant movement and massive earthquakes.

Question 24

Relationship between interations at plate boundaries and mountain building, volcanic and earthquake activity, e.g of where they occur: volcanoes and plate boundaries.

Answer 24

• near the edges of tectonic plates
• bc of the movement of the plates there is a weakness int he crust and generates intense heat that can melt rock.
• diverging plate bounaries= weakness in crust
• bc seperating plates thin the crust and lowers the pressure of the asthenosphere so it melts and magma formed goes through the weakness.

e.g. Krakatoa: volcanic island in Indonesia lies on the convergence of Indian-Australian and Eurasian plate
- converging bounrdaies (suduction occurs) = weakness in crust
- under the sea there is a chain of volcanoes.

Question 25

Relationship between interations at plate boundaries and mountain building, volcanic and earthquake activity, e.g of where they occur: Earthquakes

Answer 25

• rapid movement of the gorund in wave motions caused by rapid relase of energy as tectonic plates move
• friction must be overcome before they move
• when great enough force, they suddenly move bc plates can no longer hold.
• sudden movement dsends out waves of energy
• the ground and water shakes as waves of energy pass through them.
• strongest occurs near converging plate boundaries: plate tectonics

e.g. Tokoku Japan
- converging boundary pacific plate subducting beneath the NA plate.

Question 26

Relationship between interations at plate boundaries and mountain building, volcanic and earthquake activity, e.g of where they occur: Mountain building.

Answer 26

• convergent boundaires
• continental plat collision: pushing against each other
• fold and uplifts the crust to form mountian ranges
• oceanic plate subducts beneath continental plates = heat and pressure
• the continental plate bucks to form mountain ranges

e.g. Himalayas:
collision of Indian plate and eurasian plate

Question 27

epicenter

Answer 27

• the point on the searths surface directly aboce the epicenter, where the effects of the earthquakes are most intense

Question 28

focus

Answer 28

• the point within the earth where the earthquake originates, located at varying depths.

Question 29

Types of earthquake waves

Answer 29

• Primary waves = p-waves: longitudinal waves that travel fast through the earth, shaking the ground up and down.
• secondary waves = s-waves:
  transverse waves that travel slightly lower than P waves, shaking the ground sideways and back and forth.
• Surface waves
  Slowest waves that travel along the earths crust, causing the most destruciton can be much larger than the others.

Question 30

Instrument used to meausre earthquakes.

Answer 30

Seismometer
- uses the principle of inertia which is the inherent property of a body that makes it oppose any force that would cause a change in its motion
- old style is a pen on a mocing drum
- haavy mass attache to the pen has.a lot of inertia which means it tends to stay still and the rest of the seisometer moves with the vibrations of the earth.
- the trace of the Seismometer is the seismograph.

Question 31

earthquake magnitude and the richter scale

Answer 31

• earthquake magnitude is measured on the richter scale.
• the richter scale quantifies the energy realsed during the earthquake
• each wole num increase represents 10 times the increas in the amplitude
• this scale is used to classify earthqakes, the higher the value the more powerful the earthquake.

Question 32

formation and features of hot sport volcanoes with those formed at diverging and converging plate boundaries.- hot spot volcanoes

Answer 32

formation
- form away from plate boundaries over “hot spots” where these is a magma plume beneatht he earths crust.
- allows hot magma to rise and create a volcanic island or mountains.

features
- chain of islands as the tectonic plate moves over the hot spot and generally have a broad sheild like structure, producing balistic lava.

Question 33

formation and features of hot sport volcanoes with those formed at diverging and converging plate boundaries.-diverging boundary volcanoes.

Answer 33

• constructive boundary, the tectonic plates are moving away from each other causing new rock to form
• low, gentle sloping sides,
• formed by the eruptions fo thin. runny lava
• eruptions tend to be frequent but relatively gentle.
• shield volcanoes.

Question 34

formation and features of hot sport volcanoes with those formed at diverging and converging plate boundaries.-converging boundary volcanoes.

Answer 34

• composite volcanoes
• made up of alternating layes of lava and ash
• usually found at destructive boundaries, moving towards each other
• pyroclastic flow rather than laa meaning hot steam, ash, rock and dust.
• very high speeds and temp